A gas turbine includes a compressor that generates compressed air by compressing atmospheric air, a combustor that generates combustion gas by combusting fuel in the compressed air, and a turbine that is driven by the combustion gas. The turbine has a turbine rotor that rotates around an axis, a plurality of vane rows that are arrayed in an axial direction in which the axis extends, and a turbine casing that rotatably covers the turbine rotor. The turbine rotor has a rotor shaft that extends in the axial direction around the axis, and a plurality of blade rows that are fixed to the rotor shaft. The plurality of blade rows each have a plurality of blades that are arrayed in a circumferential direction around the axis. One vane row of the plurality of vane rows is disposed on the upstream side of each of the plurality of blade rows. The plurality of vane rows each have a plurality of vanes that are arrayed in the circumferential direction around the axis.
The blade has a blade body extending in a radial direction, and a platform provided on the radially inner side of the blade body. The vane has a vane body extending in the radial direction, an inner shroud provided on the radially inner side of the vane body, and an outer shroud provided on the radially outer side of the vane body. Each of the platform of the blade and the inner shroud and the outer shroud of the vane is a flow passage forming plate that defines a part of a gas flow passage through which combustion gas flows. In addition, ring segments that constitute a part of the turbine casing and are disposed on the radially outer side of the blades are also flow passage forming plates that define a part of the gas flow passage.
Each of these flow passage forming plates is exposed to high-temperature combustion gas, and therefore needs to be cooled with cooling air, for example.
For example, Patent Literature 1 below discloses a technique of cooling the inner shroud of a vane, which is a flow passage forming plate, with cooing air from the radially inner side of the inner shroud. This inner shroud has a shroud plate main body and a peripheral wall that is provided along a peripheral edge of the shroud plate main body. The shroud plate main body has a gas path surface facing the side of a gas flow passage through which combustion gas flows, and an inner surface facing the opposite side from the gas path surface. The peripheral wall protrudes toward the radially inner side relative to the inner surface of the shroud plate main body. This inner shroud has an impingement plate provided inside a region surrounded by the peripheral wall, at a position, separated from the inner surface of the shroud plate main body toward the radially inner side. This impingement plate has a plurality of through-holes. This impingement plate is supported by a ledge that protrudes along an inner wall surface of the peripheral wall, from the inner surface of the shroud plate main body toward the radially inner side.
Cooling air is blown out of the plurality of through-holes of the impingement plate toward the inner surface of the shroud plate main body. Thus, the shroud plate main body having the gas path surface is impingement-cooled by this cooling air.